If I can buy X for $1.00 from location A and sell it for $1.01 at location B, then the only thing I need to worry about is what happens if the price moves again

If I can buy X for $1.00 from location A and sell it for $1.01 at location B, then the only thing I need to worry about is what happens if the price moves against me at either A or B between the time I send my orders and the time they're accepted. I guess you could technically call that "trying to read the future", but the (big) difference is that the horizon is on the order of probably a few milliseconds at most, not 5 minutes.